I am in the process of developing a universal simulator. USim or SimU, in which the base program is the universe, and the add-ons are what you like.....if you like planes you can design, build, and fly them, if you like cars you can design, build, and drive them, if you trains you can design, build, and conduct them, boats, etc., etc.,.....oh yeah if you like space stuff you can design, build, and orbit, explore, and inhabit the universe. It is kind of like "Second Life", but realistic and for the whole universe.